Rock-drilling bit.



T. CONNELL. ROGK DRILLING BIT.

, APPLICATION FILED JULY 21, 1909.

Patented Oct. 18, 1910.

s'r s PA. E OFFICE.

TEBRENCE GONNELL, OF HAVERFORD, PENNSYLVANIA.-

ROCK-DRILLING BIT. 7

Specification of Letters Patent.

Patented Oct. is, 1910.

Application filed July 21, 1909. Serial No. 508,811.

more particular reference to a bit of that general type in which anumber of radially disposed end cutting teeth are provided.

The object of the invention is to provide a bit of the above type inwhich the work is performed with a minimum expenditure of power and aminimum degree of resistance to the action of the cutting teeth. Thisobject is accomplished by providing .a bit of such construction that apartial cutting and a partial grinding effect is produced in a novelmanner, the grinding or crushing -action being an incident of theordinary feeding and turning moments of the bit. Cone sequently, in thepresent construction a result i's incidentally accomplished which in theordinary constructions is objectively ac complished: It follows from theforegoing statement that the actual cutting area may be considerablyreduced andtherewith is had a reduction of the resistance encountered bydriving the bit into the rock, the

crushing or grinding action being, as stated,

incidental, and'ofl'ering very little and a far less degree ofresistance to the bit than would be the case if the area to which thecrushing action is confined, were cut,\ as in spective view of a rockdrilling bit con;

structed in accordance with the present invention. Fig; 2 is an endelevation thereof. Fig. 3 is a longitudinal sectional view thereof onthe-line 33 of Fig. 2 and Fig.4 is a similar view thereof on the line4-4 of Fig. 2. imilar characters of reference designate correspondingparts throughout the several views.

The shank of the bit is indicated by the numeral 1 and is preferablyconstructed with a constricted axial duct, as 2, through ticallycompletel inclosed which a liquid or fluid may beforced or drawn, tocarry away the dust producedas an incident of the operation of the bit.The

said shank has at its working end, out

Wardly diverging ribs or facets, as 3, which i may be of any desirednumber and arrangement and between which clearance grooves, as 4, forthe passa e of the aforesaid dust laden liquid or flui occur, Thegrooves .4 terminate at their outer ends in inversely curved facets, as5, which extend forwardly in convergent relation for, a comparativelyshort distance. The inner edges of the facets 5 are indicated by thenumeral 6 and are also the bounding edges of a recess or 0 ening 7 whichis of inwardly tapering orm and extends axially of the drill, the innerend of the recess or opening 7 meeting and being axially alined with theduct 2. Theapices occurrin at the junction of the inversely curved acets5 are sharpened to constitu'te radial cutting teeth, as 8, which extendfrom the corners formed by the. junction of the edges 6, to the medianlongitudinal lines of the ribs or facets 3.

The aforesaid recess or o ning7 is pracb; the surrounding portions of te drill and consequently a maximum grinding and crushing area isafforded. Incidentally the ed es 6 may be and. preferably are sharpeneto constitute cutting blades.

* The arrangement herein shown is preferred, though not obligatory. Inthe present arrangement-I employ four ribs or facets 3, a correspondingnumber of facets 5 and of teeth 8, a rectangular mouth bounded by.pyramidalform, as a consequence .of which a series of lines drawn atdifferent angles through the center of. said opening by a comparison ofthe wi ths of the opening in the two lanes through which Figs. 3 and 4are ta en. -The result of this is that the crushing pressure isgradually increased after its initial application and it follows that a.more efiicient crushing action is produced than would be the case if thecrushing pressure were uniform.

In use, the teeth 8 will have a cutting action on an'annuhr area, thewidth of which is determined by the extent of said teeth. At the centerof this annular cutting area a pinnacle is left and this pinnacle isworn away as the bit is advanced by will be of successivelyvar ying lenhs, as 1s shown virtue of a combined cutting and crushing action, thecutting actionbeing produced by the edges 6 which take off the cornersand sides of the pinnacle and the crushing action being produced by thetapered form of the opening or recess 7, the walls of which receive thesaid pinnacle in a wedge-like engagement of constantly increasingpressure which is exerted both axially by virtue of the tapered form ofthe recess and also laterally by virtue of the square cross section orpyramidal form of the recess.

It follows from the, foregoing description that the advantages stated inthe introductory paragraphs are efficiently attained, since the deviceoperates with a minimum cutting area and a consequent minimum resistanceand with a maximum crushing area ofi'ering far less resistance than theequivalent cutting area found in the devices now known in the art. Thestructure incidentally preserves all the advantages of the known deviceswhile adding thereto the novel advantages above set forth.

formation thereof throughout the cutting operation.

2. A drill bit having its working face cutting o eration and the recesshaving a suflicient egree of inward taper to produce the grinding downand crushing of the pinnacle continuously with the original formationthereof.

3. A drill bit having the working end of its shank formed Withxoutwardly divergent facetsand with grooves alternating with the facetsand terminating in outwardly converging facets, the apices of which aresharpened to consti'tute radial cutting teeth which extend to thelongitudinal centers of the several divergent facets, the bit alsohaving at its working end a centrally arranged inwardly tapering recess,the bounding edges of which are also the inner edges of the convergentfacets, the radial teeth producing a pinnacle on the material in whichthe cut is being made continuously throughout the cutting operation andthe recess having a sufiicient de ee of inward taper to produce thegrindlng down and crushing of the pinnacle continuously with theoriginal formation thereof. I

In testimony whereof I have hereunto set myhand. in presence of twosubscribing witnesses. I

TERRiaNoE CONNELL."

Witnesses J. C. WHITBY, J. K. LEWIS.

